The test was flaky and failing with the following errors:
```
Failure/Error:
klass
.connection
.select_raw(relation.arel) do |result, _|
result.type_map = DB.type_map
result.nfields == 1 ? result.column_values(0) : result.values
end
NoMethodError:
undefined method `select_raw' for nil
./lib/freedom_patches/fast_pluck.rb:60:in `pluck'
./vendor/bundle/ruby/3.3.0/gems/activerecord-7.2.2.1/lib/active_record/relation/calculations.rb:354:in `pick'
./app/models/web_crawler_request.rb:27:in `request_id'
./app/models/web_crawler_request.rb:31:in `rescue in request_id'
./app/models/web_crawler_request.rb:26:in `request_id'
./app/models/web_crawler_request.rb:19:in `write_cache!'
./app/models/concerns/cached_counting.rb:135:in `block (3 levels) in flush_to_db'
./vendor/bundle/ruby/3.3.0/gems/rails_multisite-6.1.0/lib/rails_multisite/connection_management/null_instance.rb:49:in `with_connection'
./vendor/bundle/ruby/3.3.0/gems/rails_multisite-6.1.0/lib/rails_multisite/connection_management.rb:21:in `with_connection'
./app/models/concerns/cached_counting.rb:134:in `block (2 levels) in flush_to_db'
./app/models/concerns/cached_counting.rb:124:in `each'
./app/models/concerns/cached_counting.rb:124:in `block in flush_to_db'
./lib/distributed_mutex.rb:53:in `block in synchronize'
./lib/distributed_mutex.rb:49:in `synchronize'
./lib/distributed_mutex.rb:49:in `synchronize'
./lib/distributed_mutex.rb:34:in `synchronize'
./app/models/concerns/cached_counting.rb:120:in `flush_to_db'
./app/models/concerns/cached_counting.rb:187:in `perform_increment!'
./app/models/web_crawler_request.rb:15:in `increment!'
./lib/middleware/request_tracker.rb:74:in `log_request'
./lib/middleware/request_tracker.rb:409:in `block in log_later'
./lib/scheduler/defer.rb:125:in `block in do_work'
./vendor/bundle/ruby/3.3.0/gems/rails_multisite-6.1.0/lib/rails_multisite/connection_management/null_instance.rb:49:in `with_connection'
./vendor/bundle/ruby/3.3.0/gems/rails_multisite-6.1.0/lib/rails_multisite/connection_management.rb:21:in `with_connection'
./lib/scheduler/defer.rb:119:in `do_work'
./lib/scheduler/defer.rb:105:in `block (2 levels) in start_thread'
```
This was due to running the defer thread in an async manner which is
actually no representative of the production environment. It also
revealed a spot in our code base where writes are happening in a GET
request which can cause requests to fail if ActiveRecord is in readonly
mode.
Firstly, we need to understand that ActiveRecord can be
connected to a role which prevent writes and this happens in Discourse when a
replica database has been setup for failover purposes. When a role
prevent writes from happening, ActiveRecord will raise the
`ActiveRecord::ReadOnlyError` if a write query is attempted.
Secondly, theme fields are baked at runtime within GET requests. The
baking process involves writing the baked value to the
`ThemeField#baked_value` column in the database.
If we combine the two points above, we can see how the writing of the
baked value to the database will trigger a `ActiveRecord::ReadOnlyError`
in a GET requests when the database is connected to a role preventing
writes. However, failing to bake a theme is not the end of the world and
should not cause GET requests to fail. Therefore, this commit adds a rescue
for `ActiveRecord::ReadOnlyError` in the `ThemeField#ensure_baked!`
method.
Alan Guo Xiang Tan